Measure AC and DC Current Amps using a Hall Effect Current
Sensor Transducer

There are three key
advantages to using hall effect current sensors transducers:

They can be totally
isolated from another high voltage electrical system which eliminate risk to
delicate monitoring equipment and also minimizes
safety concerns. In other words this sensor only detects the
magnetic field around the wire, there is no electrical contact between
the sensor and the wire. This is a nice advantage over using a current monitoring
shunt precision resistor.

If your signal is
too weak or you are not
getting the resolution you want, you can simply loop the wire through the current
clamp as many times as you want to double, triple, or quadruple the
sensitivity or resolution of your sensor. For example, if your current
signal is only .03 Amps, you could loop the wire through the sensor 10
times and the signal would by 10X stronger and would appear as 0.3 Amps.

Unlike the
current shunt sense resistor which can have thermal temperature heat
dissipation issues, the hall effect current sensor does not get hot.
Even when measuring 50 Amps!

Example Wiring Diagram For the CLSA2CD Sensor Sold HERE on
Amazon.com.

The diagram above shows a 12
Volt DC wall adapter supplying voltage to a 8 Volt regulator.
The 7808 Volt regulator puts out a very stable
DC voltage. This is very important because the sensor outoput is
only ~0.032 Volts per Amp that it measures, so if the voltage you are
supplying the CLSA2CD is noisy, your data will get lost in the noise.
The ground is shared through out the circuit. You could
mount these components on a small piece of proto board
like the one shown below. Or if you want to get one already
assembled take a look at the one sold at
http://measure-current.com

Below you will
see a graph showing the relationship between current and
sensor output voltage. In this case, the sensors were mounted on
a circuit board.

The current sensor
was supplied with 8 Volts DC from an on board regulator. You can see
that when there is no current flowing through the large red wire, the
sensor simply divides its supply voltage in half (8V divided by 2 = 4.0
Volts output).

However, for every
amp that flows through the wire, the voltage output from the sensor
increased about 0.033 Volts.

The formula you
could use to convert from Volts to Amps is as follows:

Measured
Current = (Vsensor - 4.0) / 0.033

So for example if your
sensor puts out 5 Volts, then your measured current would be something like:

Below you can see real data from just one
sensor for a solar panel / battery charging application. The green
trend line represents data from the sensor. The red
trend line has been converted to Amps using the following
linear equation.
Amps = ( Vsensor - 4.0) / ~33mV

As the sun comes up, current
slowly flows into the batteries rising from 4 Volts DC to 4.5V DC.
This corresponds to a current range of Zero amps up to 16 Amps shown
in red on the right side of the graph.

When someone in the home
turns on an electric appliance then the current goes negative down
to 2.6 Volts DC because it changes direction as it flows from the batteries into the
House AC inverter which could be powering something like a
refrigerator or washing machine. A value of 2.6 Volts DC
output converts to a current value of ~ -45 Amps.
Assuming these batteries are setup in a 24 Volt configuration, then
you could use this current measurement to approximate how much power
your batteries are putting out. In this case it would be about
1,080 Watt power output to the inverter.

(24V X 45A = 1080 Watts)

Below is
an example of how you can mount a this current transducer on a
circuit board. If you want to get order information for
this device click HERE.

You can buy a hall effect transducer clamp off the shelf to measure AC and
DC current for $50 to $400. Or you can build your own.

I like the Open Loop Linear CSLA2CD model because
it puts out a linear voltage signal , and this sensor
also can detect AC or DC current. You can buy this sensor on
Amazon.com

Honeywell CS series linear
current sensors incorporate our 91SS12-2 and SS94A1 linear output
Hall effect transducer (LOHET™). The sensing element is assembled
in a printed circuit board mountable housing. This housing is
available in four configurations. Normal mounting is with 0.375
inch long 4-40 screw and square nut (not provided) inserted in the
housing or a 6-20 self-tapping screw. The combination of the
sensor, flux collector, and housing comprises the holder assembly.
These sensors are ratiometric.

This type of current sensor /
transducer requires a DC voltage to operate. For the CSLA2CD
72 Amp sensor you need to hook up an excitation voltage anywhere from 5.4
Volts to 13 Volts. I used this sensor to build a power
sequencing test rack for computers and servers. I used LabVIEW to
control HP power supplies which provided 3V, 5V, and 12V to the computers in
an environmental chamber. LabVIEW would read these Hall Effect
sensors for each of the voltages and show on a graph the exact current that
the computers and servers were consuming.

With no current going
through the loop they put out about half of the voltage you are supplying.
So if you have 10V DC supplied to this sensor, you will see about 5VDC
coming out of it. You can wire this to a data acquisition box like the
LabJACk and use a software program like LabVIEW to get waveforms like an
Oscilloscope gives you. Here is a software program I wrote using the
LabJACK data acquisition box. The picture shows 5th grade students
loved watching the power racing against each other and seeing how much power
each bike generator created:

If you want to use an off the
shelf solution you can consider something like these devices below.
BEWARE - many of these clamps measure only AC current. So check the
specifications to make sure it says AC/DC like these ones below. You
will find the AC/DC current clamps are more expensive than just AC current
clamps.

This
is a inexpensive hall effect transducer current monitoring clamp and
voltage meter. The Loop that you see is called a "Clamp".

To use it, just push
down on the lever shown on the left and the clamp opens.
Then you put it over one of your wires coming from the generator.
Power = voltage times amps. So when you get measure the amps
going through the wire, then multiply it times how much voltage is
coming out of your generator. That gives you watts.

This fluke current clamp can be used to
do continuous AC or DC current
monitoring either with your hand held DMM digital multi-meter or you
can also use a USB data acquisition device like the
LabJACK U12 (shown below) which will allow computer software to act as
a power monitor software oscilloscope. When you download the
free software for this LabJACK, it comes with free voltage monitoring
applications called "LJstream1" and "LJsimplelog". This will plot and data log your power
generated. LJsimplelog
will log data from 8 Analog input channels at a rate of 25 samples per
second. This LJsimplelog is usually fine for most DC power
applications, but is too low of a sample rate for AC power which
usually runs at 60 hertz or more. If you want a faster
data logging program, i can write one for you using LabVIEW.
Send me an email at
support@scienceshareware.com

FYI: For current voltage and power data logging to tab delimited text
files or chart recorder, you will want to do continuous analog voltage
signal to hook up to a data logger so you can monitor current or power
over a few hours or even days time. The graph shown in the
image below and on the projector white -screen in a class room
activity is giving what they call "Real Time" voltage / Current /
Watts plot data. Power = Amps X Volts so you have to monitor
current and voltage and then multiply them times each other to get
Watts.

This would allow you to calculate KW
Hours to see how much total power has been used or created.